1. Field of the Invention
The present disclosure relates to a light emitting device.
2. Discussion of the Background
Light Emitting Devices include P-N junction diodes that convert electrical energy into light energy. The diodes are formed by combining group III and V elements on the periodic table. Light Emitting Devices can also emit various colors by controlling the composition ratio of compound semiconductors.
In more detail, when a forward voltage is applied, an electron of an n-layer is combined with a hole of a p-layer to emit energy corresponding to an energy gap between the conduction band and the valance band. The energy is then emitted as light.
In addition, nitride semiconductors, for example, are being considered for the fields of optical devices and high-power electronic devices, because of their high thermal stability and wide band gap energy. In particular, blue LEDs, green LEDs and UV LEDs that use nitride semiconductors are available. Further, the light emitting devices may be categorized into a horizontal type and a vertical type.
Also, an N-type electrode and a P-type electrode are disposed over/under related-art vertical light emitting devices, respectively. In this instance, electrons and holes injected by the N-type electrode and the P-type electrode, respectively, are entered into an active layer, and are combined with each other to generate light. The generated light is then emitted to the outside or is reflected by the N-type electrode and lost.
Thus, related-art light emitting devices have a limitation in that the light emitting efficiency is reduced, because light emitted under the N-type electrode is reflected by the N-type electrode. Also, related-art light emitting devices have a limitation in that excessive heat is generated due to the re-absorption of the light reflected by the N-type electrode. Moreover, related-art light emitting devices have a limitation in a deterioration of life span and reliability because of current crowding.